1

What pHe3 can teach us Polarized He-3 is an effective neutron target d-quark

target Polarized protons are an effective u-quark target

Therefore combining pp and pHe3 data will allow a full quark flavor separation u, d, ubar, dbar

Two physics trusts for a polarized pHe3 program: Measuring the sea quark helicity distributions through W-production

Access to Ddbar Caveat maximum beam energy for He-3: 166 GeV

Need increased luminosity to compensate for lower W-cross section

Measuring single spin asymmetries AN for pion production and Drell-Yan expectations for AN (pions)

similar effect for π± (π0 unchanged)3He: helpful input for

understanding

of transverse spin phenomena

Critical to tag spectator protons from 3He with roman pots

2

eRHIC: polarized eHe3 scattering Future:

Polarized electron – proton and electron – He3 scattering allows for a test of the best know Sum Rule in QCD

The Bjoerken Sum Rule

Calculated in pQCDCurrently measured to 10%

EIC could provide a 1-2%measurement, if beam polarization Is measured to 1-2%

g1p and g1

n: polarized structure functions

More insights to the proton

E.C. Aschenauer He-3 Workshop, BNL, September 2011

Unpolarized distribution function q(x), G(x)

Helicity distribution function Dq(x), DG(x)

Transversity distribution function dq(x)

Correlation between and

Correlation between and

Correlation between and

Sivers distribution function

Boer-Mulders distribution function

Single Spin Asymmetries

beyond collinear pictureExplore spin orbit correlations

3

E.C. Aschenauer He-3 Workshop, BNL, September 2011 4

Dq: W Production Basics

u 　　

d

Since W is maximally parity violating W’s couple only to one parton helicitylarge Δu and Δd result in large asymmetries.

No Fragmentation !

Similar expression for W- to get Δ and Δd…

5

de Florian, Vogelsang

expectations for ALe in pp

collisions

E.C. Aschenauer He-3 Workshop, BNL, September 2011

t large u large

strong sensitivity to

t large u large

limited sensitivity to

E.C. Aschenauer He-3 Workshop, BNL, September 2011 6

ALW: Future Possibilities

Can we increase p-beam energy? 325 GeV: factor 2 in sW

access to lower x for Dg(x)

Increased beam-energy and polarized He-3 beam full flavor separation

ALW:

pp

@ 5

00 G

eV

ALW

: H

e3-p

@ 4

32 G

eV

phase 2 of pp2pp@STAR can separate scattering on n or p

Quantum phase-space tomography of the nucleon

3D picture in momentum space 3D picture in coordinate space transverse momentum generalized parton distributions dependent distributions exclusive reaction like DVCS

E.C. Aschenauer He-3 Workshop, BNL, September 2011 7

Polarized p d-quarku-quark Polarized p

Join the real 3D experience !!

TMDs GPDs

Wigner DistributionW(x,r,kt)

d3 r

d 2ktdz

E.C. Aschenauer He-3 Workshop, BNL, September 2011 8

AN in 3He-proton collisions Sivers fcts. for u and d quarks opposite in sign and slightly larger for d quarks

Z. Kang @ 2010 Iowa RSC meeting

• u <-> d isospin rotation leads to different signs for AN for protons and neutrons

• asymmetries for neutrons are larger (due to electric charges)

expectations for Drell Yan

proton

neutron

expectations for AN (pions)

• similar effect for π± (π0 unchanged)

this time computed within twist-3 formalism here, effect due to favored/unfavored fragmentation

caveat:does not yet includepossibility of nodesin Sivers function

3He: helpful input for understanding

of transverse spin phenomena

The long term future future of pp@RHIC